The present invention relates Doppler processing. In particular, methods and systems for automatically adjusting imaging parameters for either of radiology or cardiology Doppler imaging is provided.
For spectral Doppler imaging, a pulse or continuous wave is transmitted to a particular location in a patient. The signals received are processed using a fast Fourier transform or other frequency analysis. The resulting Doppler spectrogram shows the range of velocities modulated by an associated energy or spectral power as a function of time for the gate position. The data for each spectral line or time comprises multiple different frequency or velocity intervals where each of the frequency intervals is modulated by the spectral power for the interval, representing an instantaneous measurement of blood flow at the gate position.
Various system settings or imaging parameters affect the display of the Doppler spectrum. The pulse repetition frequency, the baseline level, the gain and the dynamic range applied by the system alter the display of the Doppler spectrum. For example, the pulse repetition frequency or velocity scale may be set to avoid aliasing while maximizing the information content or number of velocity intervals used in the displayed spectrum. As another example, the gain and/or dynamic range may be set to minimize information loss due to saturation or compression to a few values. As yet another example, the baseline may be set such that the positive or negative information are displayed with a relative amount of content, minimizing the velocity scale.
Any of the various system settings are typically controlled by the user. Some systems may automatically adjust the scale, baseline, or other parameters. Data is acquired at the user""s initial or later settings, adversely affecting the performance of the automatic optimization. In one such system, a maximum and minimum trace on the envelope of the Doppler spectrum is used to determine a new pulse repetition frequency. However, artifacts in the maximum or minimum trace may adversely alter the determined pulse repetition frequency, resulting in excess unused capability of imaging the Doppler spectrum.
The present invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims. By way of introduction, the preferred embodiments described below include methods and systems for automatic optimization in Doppler ultrasound imaging. One or more of the velocity scale (e.g., pulse repetition frequency), gain, baseline, dynamic range or other imaging parameters are optimized based on one or both of: (1) determining the optimum parameter based on signal acquired at a standard or predetermined setting of the parameters and (2) identifying an artifact in the Doppler ultrasound data and discarding or minimizing the influence of the artifact on any determination of imaging parameter settings.
One embodiment used for cardiac Doppler imaging identifies artifact signals using the maximum or minimum velocity traces. For example, the velocity scale or pulse repetition frequency is set based on the maximum or minimum velocity value over one or more heartbeats identified from a maximum and minimum trace of the signal envelope or Doppler spectrum. Since flows in cardiology may contain high energy, high velocity, short duration signals caused by valve clicks, these artifacts are identified and discarded in determining the maximum and minimum velocity values.
In a first aspect, a method for automatic optimization in Doppler ultrasound imaging is provided. At least one signal or a plurality of signals from a gate position in a patient are identified. The identified signal is discarded from the plurality of signals. At least one of a pulse repetition frequency, a baseline position, a gain and a dynamic range is automatically set as a function of the plurality of signals after substantially discarding the identified signal.
In a second aspect, a system for automatic optimization in Doppler ultrasound imaging is provided. A Doppler processor is operable to detect a plurality of signals corresponding to a gate position in a patient. An optimization processor is operable to identify at least one signal from the plurality of signals, substantially discard the identified signal, and automatically set an imaging parameter or display characteristic as a function of the plurality of signals after substantially discarding the identified signal.
In a third aspect, maximum and minimum velocity traces are determined in a Doppler spectrum as a function of time. Portions of the maximum and minimum traces corresponding to a valve click are identified. A imaging parameter is automatically set as a function of the maximum and minimum traces without the identified portions.
In a fourth aspect, a method for automatic optimization and Doppler ultrasound imaging is provided. Spectral Doppler information is acquired in response to predetermined imaging parameters. One or more of the predetermined imaging parameters are automatically reset as a function of the spectral Doppler information acquired in response to the predetermined imaging parameters.